Electric alarm system



, March 28, 1956 SPERRY 2,591,793

ELECTRIC ALARM SYSTEM Filed May 31, 1947 '29 52 3840 14 T l6 15v V 2 nJ, I V3 I0 T INVENTOR. ALBERT F SPERRY BY I Patented Mar. 28, 1950UNITED STATES rA 'rENT- orricr.

Albert F. Sperry, Chicago, .111.

Application May 31, 1947, Serial No.*7=51,503

This invention :relates to an alarm system for the "supervision of aplurality of apparatuses.

A general object of this invention is to provide an electric alarmsystem which is of simple construction, reliable in operation andself-resetting,

activefor the duration of the abnormal @condition in .the apparatus, butis automatically reset for a next operation of the common alarm devicewhen the condition .in theappa-ratus has returned to normal.

,It is a further object of the invention to prov-ide an automaticallyresetting :alarm system of the .kindjust described wherein the circuitcontaining the acommonr'alarm device can be :manual- ,ly broken by meansof a .single switch, :5. g. :a

push-button switch, regardless of which signal circuit has :put thealarm into operation.

Another object'of the invention is atoprovide an alarmsystem "wherein aplurality of signal circuits, each comprising -,:a normally closedswitch,

work in parallel upon a common alarm device and, when one of thesesignal circuits has .zactuated the alarm device, the switch that signalcircuit opens after some time lag without inter 'feri-ng with theenergized alarm device which has 2130 be cut out by hand-and isthereafter ready again for becoming actuated by-any one ,of the signalcircuits to the exclusion of that particular signal circuit which:caused the operation .of the j alarm device before.

It is a further object of the invention to provide .in :an electricalarm system for the supervision of a plurality of apparatuses anormally open alarm circuit controlled by a relay upon whichseveralj-s'ignal circuits operate in parallel, each of these signalcircuits containing switch means which,;in consequence of the occurrenceof a faulty Iconditiori in the coordinated apparatus, first close andthen, after a time lag, inactivate the signal circuit.

,i inot her object of the invention is to provide in combinationwithcontact devices having ,a-movable means .for keeping each signalcircuit inactive as long as the condition in the coordinatedappara'tusis normal and activating it upon the gOQQU-IIEHOB ofabnormality of .saidcondition, 2a

13 Claims. (Cl. 177311;)

permanently illuminated lamp and shutter means which are movable .by themovable means "of the coordinated contact device to indicate visuallywhich particular signal circuit \or circuits is or have been actuatingthe audible alarm.

.A further object is to provide in an electric alarm System of the typereferred to, wherein :a movable part of the contact device of at leastone of the signal circuits .is put into action ,by either one of twoabnormal conditions, such pressure above a prescribed value andundenpressure below the :same or .a different prescribed value, optical:signal means which comprise :a movable element moving in unison withsaid movable part of the contact device so as to indicate visuallynot-only which particular signal aircui-t or circuits is or have beenactuating the audible alarm, but also what kind of abnormal conditionprovoked the operation ofthe zalarm.

A still further object of the invention is to provide in anelectricalarmsystem having a normal- .ly open alarm circuit controlled by a relayupon which several signal circuits operate in parallel, ,a controlcircuit for each signal circuit whichiis independent of ,said relay andwhich, .after the signal circuit has been activated due to theoccurrence 10f an abnormal condition in the coordimated apparatus, rendersthis signal circuit inoperative on rtherelay andkeeps it .so inoperativeuntil the condition in the apparatus .is back to normal.

in one particular embodimentof the invention theswitch means in eachsignal circuit comprise a thermal switch operable by a heater elementwhich forms part of a control circuit that becomes energized upon theoccurrence-of a faulty condi- $1011 in the coordinated apparatus andstays ,so energized during the time the faulty condition persists, nomatter what the position of the ther mal switch and/or the condition ofthe common alarm circuit is.

Where control circuits of the kind just rel-ferr-ed team to be used, itis a further object of the invention to provide means which will .keepthe heater element from overheating, but will permit it tooperate atvfull strength upon :the thermal switchsduring the period the ,heaterelement is operative to open said switch. 7

Other objects 0f the invention will appear as the description proceeds,reference being :had tothe accompanying drawing in which:

.Eig. l is a wiring diagram showing by way of example one ,form of analarm system embodying the present inventiongand Figs. .2 and .3,respectively, show schematically a two-way pressure responsive alarmactuating unit and a single-action alarm actuating unit, each of theseunits comprising also optical indicating means.

Referring first to Fig. 1, the reference numerals It, H and I2 denotethree supply mains connected respectively to the end terminals l3, l4and an intermediate point |5 of a suitable electric current source, suchas the secondary winding l 6 of a transformer. The supply main ID isgrounded and forms the return lead for the main I l as well as for themain l2, the voltage V2 across the.

mains I0, |2 being lower than the voltage V1 across the mains ID, I

An alarm circuit is provided between the mains l0 and I I, this alarmcircuit comprising an operating coil ll of an alarm device l8 of anysuitable kind, preferably, as shown, an acoustic device, further arelatively high-resistance main relay 9 with armature 23 adapted toclose two normally open contacts 2|, 22, and a manually operable cut-outswitch 23, such as a push-button switch, permitting the temporaryopening of two normally closed contacts 24, 25.

Cooperating with the normally open alarm circuit just described areseveral signal circuits, each being coordinated to one of severalapparatuses so that the common alarm device l8 will be operated upon theoccurrence of irregularities in the operation or condition of any one ofthese apparatuses. In Fig. 1 there are shown three such signal circuits,but any other number of apparatuses may be served by the common alarmcircuit. Each signal circuit contains a switch device,

generally denoted as 26, 21 and 28, respectively,

adapted to open with a certain time delay, and a contact device,generally denoted as 29, 33, and 3|, each cooperating with one of theswitch devices 26, 21 and 28. The time delay with which the switchdevices 26, 2! and 28 are intended to operate may be realized in one ofvarious ways, well known in the art of making time delay switches orrelays, and in the example shown thermal switches are used, eachcomprising a contact pair 32, 33 which is operable by a heater coil 34.Each contact 32 is connected to a contact of the coordinated contactdevice 29, or 3| as will be presently described, whereas the contacts 33are connected in parallel to a lead 35 which in turn is connected to asuitable point of the common alarm circuit, such as to the contact 2|.The heater coils 34 are each connected at one end to a contact of thecoordinated contact device and at the other end to the low voltagesupply main l2.

The contact device 29 for the switch device 26 comprises a double poleswitch 4|! which may move between two end positions, in the one endposition closing a pair of contacts 36, 37 and in the other end positionclosing another pair of contacts 38, 39. Contact 36 is connected tocontact 38 and contact 31 to contact 39 and the switch 40 is connectedby a lead 4| through a resistor 42. to the grounded supply main Ill. The

the

switch device 27 is shown as being of the same type as the contactdevice 29 and for that reason the same reference numerals are used forboth contact devices 29 and 39. However, the pipe leading from thebellows 44 to the apparatus to which the contact device 30 iscoordinated is given a different number, 46, to indicate that this pipeleads to another apparatus than the pipe 45.

The contact device 3| is in the form of a relay 63 controlling by itsarmature 64 two pairs of contacts 65, 68 and 61, 68. The armature 64closes both contact pairs 65, 66 and 61, 68 when the relay coil 63 isenergized and opens both contact pairs when the relay becomesde-energized. A

F switch 49 adapted to connect two contacts 50, 5|

in a lead 52 connecting one end of the relay coil 63 with either themain H or the main l2, in the example shown with the main H, is operableby a member 53 which is actuatable for closing the contacts 50, 5| whena selected condition in the apparatus with which the member 53 is inoperative connection becomes abnormal. The other end of the coil 63 isconnected to the supply main I9 by means of a lead 54. Connected betweenthis lead 54 and the interconnected contacts 66 and 68 is a resistor 55.The contacts and 61 are respectively connected to the contact 32 and toone end of the heater coil 34 of the switch device 28.

The operation of the signal system thus far described is as follows:

As long as the conditions to be supervised in the various apparatusesare normal, the switches 40 or 64in the contact devices 29, 39, 3|,etc., are all in their inactive position shown in Fig. 1. Assuming nowthat a faulty condition occur in the apparatus connected by the pipe 45to the bel-- lows and that this faulty condition consists in anoverpressure, then the bellows 44 will expand, moving by means of theelement 43 the double pole switch 40 into contact with the contacts 38and 39. Thereby a signal circuit is established which can be traced fromthe grounded supply line In over the resistor 42, the lead 4|, switch40. contact 38, contact 38, the closed thermal switch 32, 33, lead 35,point 2|, the main relay coil l9, and the closed contacts 24, 25 to thesupply line At the same time a circuit through the heater coil 34 isestablished which extends from line l0 through the resistor 42, the lead4!, the switch 40, the contacts 39 and 31, and the heater coil 34 to thelow voltage supply line 2. The energized main relay coil l9 attracts itsarmature 20 so as to connect the contacts 2|, 22, inserting thereby thecoil I of the acoustic alarm device 3 into the circuit. The alarmcircuit thus established remains closed and keeps the signal sounding aslong as it is not manually opened by means of the push-button switch 23.Opening of the thermal switch 32, 33 under the heating action -of theheater coil 34 will not open the alarm circuit.

As the armature 20 of the main relay I9 connects the contacts 2| and 22and thereby establishes the alarm circuit, the resistor 42 isautomatically cut out and remains ineffective as long as the thermalswitch 32, 33 remains closed. During that period a circuit through theheater coil 34 by-passing the resistor 42 is established which can betraced from the main |0 through the low resistance signal coil H, thecontacts 22, 2| closed by the armature 20, the closed thermal switch 33.32, contact 38, switch 40, contacts 39 and 31 and through the heatercoil 34 to the low voltage main l2; Thus, while the heater 001134 isenergizedvia the resistor '42 for that short interval between theclosing of the contacts 38 and 39 or 35 and i-iil by the double poleswitch 40, and the closing of the contacts 21 and 22 by the armature '2s ofthe relay 1'9, the resistor 42 is inoperative for the pe-- riod theheater coil operates to open the thermal switch 32, '33, that is to say,when a strong heating effect is actually desirable. When the heatingefiectof the heater soil on the thermalswitch reaches the point wherethe thermal switch opens and thereby breaks'the justdescribed'heating.c'ir cuit by-pa'ssing the resistor 42, that heating circuit includingthe resistor 42 is re-established which existed before the relayarmature 2ilconnected the contacts 2! and 22. Now "the heater coiloperates at Ya reduced temperature due to the resistor 32 being inseries with "the heater coil. From the moment on, therefore, when thethermal switch 32, 3'3 opens, the heater coil operates at a temperaturewhich, while being sufficient to keep the thermal switch open, is lowenough not to overheat'the heater coil even during a period of hours ordays. "This reduced operating temperature of the heater coil alsopermits the latter to cool down :quickly to the temperature at which thethermal switch closes when. due to the fact that the condition in thecoordi nated apparatus has been restored to normaLthe double pole switchto returns to its neutral positionshown in Fig. 1.

As has been mentioned before, the alarm circuit through the coil llremains closed after the thermal switch '32, 33 of the switch device 2 6has been opened by the :action ofits heater coil 34. To silence 'thealarm device 1 8 the push-button switch 23 is pressed down manually.This breaks the circuit containing the relay coil 19 which is thusdeeen'ergized and releases the armature "2'0 to open the contacts 21!,22 in the alarm circuit through the alarm device coil I1. Upon releaseof the push-button switch 23 the main relay is is ready again foractuation by any of the signal circuits of the device with the exceptionof the signal circuit belonging to the contact deV'ice Z-Q which, aslong as the irregularity of condition persists in the coordinatedapparatus, remain in- "terruptedatthe open thermal swit'ch 32 33. Anyother act the contact devices 3!), 3'1, etc, however, upon receivingfrom its coordinatedapparatus-the impulse caused by a faulty conditionin that apparatus which will cause its movable member All or -54 to movefrom its neutral position shown in the drawing into a contact-closingposition, will cause energization of the main relay is and the alarmcircuit the same manner as has been described in connection with theswitch device 25.

The actuation and operation of the alarm circuit is basically the samewhether the switch 'devices are put into operation by :a contact deviceof theikind shown :at 29 or at oroi the'kind'shown v:at 3.]. It istobenote'd, however, that the double pole switch arrangement of thecontact devices '29 and 3 is operative both at a given "maximum as wellasat a given minimum'value of the condition to be controlled, whereasthe armature t of the contact device 13! operates with one off- {and one'0n'-po'sition only. In the example :s'hown the double pole switch 48cooperates with a bellows (which may be replaced by some other,ilui'dpressure responsive device) so as to close the :one contact pair:38, 39 when a certain -overpres sure is reached and :the other contactpair 36, 3 when a certain nnderpressure occurs, 'whereas it occupies aninactive position as longias :th -pressure is within the allowed range.In contrast thereto the armature 64 of the contact device 3% alwayscloses or opens all the four contacts '65 to 68 simultaneously, closingthem when the condition to be supervised in the coordinated apparatuspasses a predetermined value in one given direction. Assuming, forinstance, that the :condition to be supervised is the liquid level, thearrangement may be such that the member 53 moves the switch 49 to closethe contacts =50, :51 in the line 52 when the liquid level in the.apparatus falls below a given minimum level but keeps the "contacts 50,5! open without regard to any height of the liquid level above thatprescribed minimum level. Or, the member :53 maybe connected to theinterior of the coordinated apparates in such a manner as to close theswitch 49 when the'liquid level rises above a certain prescribed maximumheight, whereas the switch 63 is 'kept open as long as the liquid levelremains below that height. When in either case the member 53 moves theswitch 4:9 into its closing position the relay coil '53 :is energized.and pulls its armature 54 into the position in which itconmeets thecontact 65 with the contact 56 and the contact 61 with the contact 168.When the ccndition in the coordinated apparatus has become again such asto allow the member 53 to return to the position in which it keeps the:switch 459 open the coil 63 becomes de-energized, and the heater coil34 of the switch device 28 is :cut out. permitting the thermal switch32, '33 of this device to reset "itself for :a next actuation of "themain relay [9 should another irregularity of the supervised conditionoccur in the same apparatus.

With each contact device 29, 30, 31, etc, means are combined forindicating visually which particular signal circuit is or has beenactuating the audible alarm signal It. These visualmeans include a "lampand a light intercepting member which is movable between said lamp and awin- (low or sight opening provided in the wall of a panel board' orbox. Fig. 2 shows diagrammati cally-an optical {indicating device operatively con-- nected with a contact device of the kind shown in Fig. 1at 29 "(or '35). The contact device 29 togather with the switch device'26, the bellows M and the resistor 12 are housed in a signal box havina sight opening or window H. Behind that sight opening 1| a lamp l2 islocated which is connected between "the grounded supply line 1-0 and oneof the supply lines "H or l2, here the low voltage line l2, soas'tobe'permanently illumina ed. A transparent segment 73 is pivoted onan axis '14 and may be swung about that pivot by mean's'of :a leverwhich, through a link H5, :is connected with the member 43 andmoves inunison therewith, "The central portion 7'! of the transparent segment'13 may be white, whereas the two end portions 118 and is of the segmentmay be colored in two different colors, such as red and green,respectively. As long as the condition in the coordinated apparatus isnormal, which means that the double pole switch is in its neutralposition, alsothe segment 73 is in its neutral position shown in whichthe white portion "H is between the lamp l2 and the sight opening "H ofthe box 10. If the pressure in the apparatus rises the "bellows Mexpands and by means of [the member 4-3 moves not only the switch Mlinto contact with the lower contact "pairs 38, #39, but also turns,through the intermediaryof the leverage i6, 15, the segment'it in theclockwise -direction, bringing thereby the red colored portion of thesegment between the lamp l2 and the window H. This window appears now inred color, indicating that, in the apparatus to which this particularbox 10 is coordinated, an overpressure exists. Assuming that in allother apparatuses the supervised conditions are regular, the windows ofall other signal boxes will be illuminated white, whereas the sightopening H belonging to the box 10 just described will stand out by itsred color, thereby indicating in a conspicuous manner which apparatushas operated the alarm. When the attendant opens the pushbutton 23 tostop the alarm signal this will not influence the position of thesegment I3 which remains in its overpressure indicating positionregardless of the condition of the alarm circuit and regardless as towhether the thermal switch 32, 33 is still closed or is in its openposition. The segment will remain in this position until the conditionin the coordinated apparatus is returned to normal, whereupon thesegment 13 re sumes its neutral position together with the double poleswitch 40.

In case underpressure occurs in the coordinated apparatus causing theswitch to close the upper contact pair 36, 31, the segment 13 is movedin anti-clockwise direction bringing the green portion 18 between thesight opening 1| and the lamp 12 so that this sight opening appears ingreen color.

If at any time sounding of the alarm is caused by one apparatus whilethe condition in another apparatus, which has actuated the alarm at someearlier time, is not back yet to normal, then both the windows Hbelonging to the two apparatuses will appear illuminated other thanwhite. By

the particular color in which each window H appears, the attendant cannot only tell which apparatuses are out of order but also of what kindthe irregularity is in each apparatus.

If the push-button switch 23 is located at some convenient central pointand the windows H are arranged side by side, e. g. near the top of thesignal panel, the attendant, when he is called by the acoustic alarmdevice l8 to operate that button, is brought in front of the illuminatedwindows H and can hardly avoid noticing which signal is operating. Buteven if he does not look at the visual signal at that time, the visualindication will persist as long as the contact device has not been resetby the return of a normal condition in the coordinated apparatus.

Fig. 3 shows a lamp and shutter arrangement as may be used incooperation with the contact device 3! of Fig. 1. Here the shutter 83 isoperated by the armature 64 of the relay 63, moving by means of a leversystem 84, 85 or the like the shutter between a sight opening 8| of abox 80 and the lamp 82 when the armature 64 is pulled into contactclosing position, and keeping the shutter outside of the range of thesight opening 8i when the armature 64 is in its neutral position. If theshutter 83 is transparent and colored in some color, e. g. yellow, thenthe sight opening 8| will appear white as long as the armature Ed is inits neutral position and will turn yellow when the armature 64 has beenattracted by the coil 63 and has thereby moved the shutter 83 in theposition in which it intercepts selectively the light rays passing fromthe lamp 82 through the sight opening 8|. The shutter 83 will not bebrought back into the elevated position shown in Fig. 3 until thecondition in the coordinated apparatus has been remedied, regardless ofopening of the thermal switch 32, 33 by the heater coil 34 or operationof the pushbutton 23 by the attendant. Since the shutter 83 has only anon and an off position, it may, instead of being transparent and coloredin some other color than white, be opaque so as to cut off completelythe passage of light from the lamp 82 through the window 8! when in oneof its two positions, in the example shown in Fig. 3 in its on positioncorresponding to the existence of an irregular condition in theassociated apparatus. This irregularity would then be opticallyindicated by a blacked-out spot on the otherwise on all windowsilluminated panel board.

While I have shown in the drawing one particular embodiment of myinvention, I desire it to be understood that various changes andmodifications outside of those already mentioned in this specificationmay be made in the details of the alarm system without departing fromthe spirit of the invention or from the scope of the appended claims.

What I claim is:

1. In an electric alarm system for the supervision of a plurality ofapparatuses, a normally open alarm circuit common to said plurality ofapparatuses, a relay'for controlling said alarm circuit, each of saidapparatuses having coordinated thereto a signal circuit for actuatingsaid relay, switch means in each signal circuit adapted to be operatedin consequence of the occurrence of a faulty condition in thecoordinated apparatus so as to first close said signal circuit forenergization of said relay and then to render said signal circuitinoperative upon said relay and hold it so inoperative for as long atime as the faulty condition perists in the coordinated apparatus, andmeans cooperating with each of said signal circuits for automaticallyresetting said switch means to the initial position upon the conditionin the coordinated apparatus being restored to normal.

2. In an electric alarm system for the supervision of a plurality ofapparatuses, a normally open alarm circuit common to said pluralit ofapparatuses, a relay for controlling said alarm circuit, each of saidapparatuses having coordinated thereto a signal circuit for actuatingsaid relay, a normally closed thermal switch in each signal circuit, aheater for each thermal switch forming part of a circuit adapted tobecome energized upon the occurrence of a faulty cond tion in thecoordinated apparatus and stay so energized during the persistence ofsuch faulty condition, said thermal switch being adapted to open uponsaid heater reaching a predetermined temperature and to stay open untilsaid heater has become de-energized in consequence of the condition inthe coordinated apparatus having returned to normal.

3. In an electric alarm systemfor the supervision of a plurality ofapparatuses, a normally open alarm circuit common to said plurality ofapparatuses, a relay for controlling said alarm circuit, each of saidapparatuses having coordinated thereto a signal circuit for actuatingsaid relay, a control circuit independent of said relay. a resistorcommon to said signal circuit and said control circuit, a normallyclosed thermal switch in said'signal circuit, a heater elementinoperative position with regard to said thermal switch forming part ofsaid control circuit, and means adapted to keep said signal circuit aswell as said control circuit inactive as long as the condition in thecoordinatedapparatus is normal and to activate both said circuits uponthe occurrence of an abnormality of said condition, the heater aromaselement irr said control circuit, uponthe latter being so activated,opening its'coordinated thermal switch and keeping'itopen until thecondition in the apparatus is restored to normal, and a by-pass patharound said resistor for shorting out said resistor during the periodsaid heater element isoperative to open said thermal switch;

4 In an electric alarm system for the supervision of a plurality ofapparatuses, a normally open alarm circuitcommon to said plurality ofapparatuses, a relay for controlling said alarm circuit, each of saidapparatuses having coordinated' thereto a signal circuit for actuatingsaid relay and a control circuit independent of said relay, a normallyclosed thermal switch in each signal circuit, a heater element in eachcontrol circuit in operative position with regard to its coordinatedthermal switch, means for keeping said signal circuit as well as. saidcontrol circuit inactive as long as the condition in the co'ordi nated.apparatus is normal and to activate both said circuits upon theoccurrence of an abnormality of said condition, the heater element insaid control circuit, upon the latter being so activated, opening itscoordinated thermal switch and keeping it open until the condition inthe apparatus is restored to normal.

5. In an electric alarm system for the supervision of a plurality ofapparatuses, a normally open alarm circuit common to said plurality ofapparatuses,arelay for controlling said alarmcircuit, each of saidapparatuses having coordinated thereto a signal circuit for actuatingsaid relay, a control circuit independent of said relay, a resistorcommon to said signal circuit and said control circuit, a normallyclosed thermal switch insaid signal circuit, a heater element inoperative position with regard to said thermal switch forming part ofsaid control circuit, and means for keeping said signal circuit as wellas said control' circuit inactive as long as the condition in thecoordinated apparatus is normal and to activate both said circuits uponthe occurrence of an abnormality of said condition, the heater el'e--ment in said control circuit, upon the latter being so activated,opening its coordinated thermal switch and keeping it open until thecondition in the apparatus is restored to normal, and a by-pass patharound saidresistor for shortingout? said resistor during the periodsaid heater element is operative to open said thermal switch.

6. In an electric alarm system for the super vision of a plurality ofapparatuses, a normally open alarm circuit common to said plurality ofapparatuses,arelay for controlling said alarm circuit, each of saidapparatuses having coordinated thereto a signal circuit for actuatingsaid relay, a control circuit independent of said relay, and a contactdevice adapted to keep said signal circuit as well as said controlcircuit inactive as long as the condition in the coordinated apparatusis normal and to activate bothv said circuits upon the occurrence of anabnormality of said condition, saidv control circuit, upon being so:activated, rendering, with a time lag, the signal circuit inoperativeupon said relay and keeping itso inoperative until the condition in theapparatus is restored to normal whereby said contact device is caused tobreak said control circuit so as torelease said signal circuit forreturn to its initial condition, and a holding contact for holding saidrelay energized after the signal circuit which actuated said relay hasbeen rendered inoperative by its coordinated control circuit.

7. In an electric alarm system for the superid vision of a plurality ofap aratuses; a normally open alarm circuit common to said plurality ofapparatuses; a relay for controlling said alarm circuit, each of saidapparatuses having coordinated theretoa signal circuit for actuatingsaid relay, a control circuit. independent of said relay and a contactdevice adapted to keep said signal circuit as well as said controlcircuit inactive aslong as the condition in the coordinated appara:-tusis normal and to activate both said circuits upon theoccurrence ofanabnormality of said condition, said control circuit, upon beingsoactivated, rendering the signal circuit-inoperative upon saidrelay andkeeping it so inoperative until the condition in the apparatus isrestored to nor:- mal whereby said contact device is caused to breaksaid control circuitso as to release said signal circuit for return toits initial condition, and? a manually operable switch in said alarmcircuit in series with said relay for de-energizing said relay soas toopen said alarm circuit and thereby to place said relay and alarmcircuit into readiness for a subsequent operation upon the activation ofa signal circuit other than any signal circuit which was renderedinoperative on accountof the existence of an abnormal condition in theapparatus coordinated to that last named signal circuit.

8. In an electric alarm system for the supervision of a plurality ofapparatuses, a normally open ala-r-mcircuit common to said plurality ofapparatuses, a relay for controlling said alarm circuit,- each of saidapparatuses having coordihated thereto a signal circuit for actuatingsaid relay, a control circuit independent of said relay and a contactdevice adapted to keep said signal circuit as well as said controlcircuit inactive as long as the condition in the coordinated apparatusis normal and to activate both said circuits upon the occurrenceof anabnormality of said condition, said control circuit upon being soactivated rendering, with a time lag, the signal circuit inoperative"upon said relay and keepin it so inoperative until the condition in theapparatus is restored to normal whereby said contact device is caused tobreak said control circuit so as" to releasesaid signal circuit forreturn to its initial condition, aholding contact for holding saidrelay'energi'zed' after the signal circuit which actuated said relay hasbeen rendered inoperative by itscoordinated control circuit, andamanually operable switch in said alarm circuit in series with. saidrelay for deenergizing said relay so as to open said alarm circuitas'well as said holding contact and thereby to place said relay, saidalarm circuit and said holding contact into readiness for a subsequentoperation upon the activation of a signalcircuit other than any signalcircuit which was" rendered inoperative on account of the: existence ofan abnormal condition in the apparatus coordinated to that particularsignal circuit".

9. In an electric alarm system for the supervision of a plurality ofapparatuses, a normally open alarm circuit common to said plurality ofapparatuses, a relay for controlling said alarm circuit, each of saidapparatuses having coordinatedv thereto a signal circuit for actuatingsaid relay a control. circuit independent of said relay, a normallyclosed thermal switch in said signal circuit, a. heater coil. in.operative position with regard to said thermal switch forming part ofsaid control circuit, and a contact device adapted to keep said signalcircuit as well as said control circuit inactive as long as thecondition in the coordinated apparatus is normal and to activate bothsaid circuits upon the occurrence of an abnormality of said condition,the heater coil in said control circuit, upon the latter being soactivated, opening with a time lag its coordinated thermal switch andkeeping it open until the condition in the apparatus is restored tonormal whereby said contact device is caused to break said controlcircuit so as to release said signal circuit for return to its initialcondition, and a manually operable switch in said alarm circuit inseries with said relay for de-energizing said relay so as to open saidalarm circuit and thereby to place said relay and alarm circuit intoreadiness for a subsequent operation upon the activation of a signalcircuit other than any signal circuit which was rendered inoperative onaccount of the existence of an abnormal condition in the apparatuscoordinated to that particular signal circuit.

10. In an electric alarm system for the supervision of a plurality ofapparatuses, a normally open alarm circuit common to said plurality ofapparatuses, a relay for controlling said alarm circuit, each of saidapparatuses having coordinated thereto a signal circuit for actuatingsaid relay, a control circuit independent of said relay, a resistorcommon to said signal circuit and said control circuit, a normallyclosed thermal switch in said signal circuit, a heater coil in operativeposition with regard to said thermal switch forming part of said controlcircuit, and contact means adapted to keep said signal circuit as wellas said control circuit inactive as long as the condition in thecoordinated apparatus is normal and to activate both said circuits uponthe occurrence of an abnormality of said condition, the heater coil insaid control circuit, upon the latter being so activated, opening with atime lag its coordinated thermal switch and keeping it open until thecondition in the apparatus is restored to normal, a holding contact forholding said relay energized after the signal circuit which previouslyactuated said relay has been rendered inoperative by its coordinatedcontrol circuit, and a by-pass path around said resistor containing saidholding contact for shorting out said resistor during circuit for returnto its initial condition, a holding contact for holding said relayenergized after the signal circuit which actuated said relay has beenrendered inoperative by its coordinated control circuit, and a manuallyoperable switch in said alarm circuit in series with said relay forde-energizing said relay so as to open said alarm circuit as well assaid holding circuit and thereby to place said relay, said alarm circuitand said holding circuit into readiness for a subsequent operation uponthe activation of a signal circuit other than any signal circuit whichwas rendered inoperative on account of the existence of an abnormalcondition in the apparatus coordinated to that particular signalcircuit.

12. In an electric alarm system for the supervision of a plurality ofapparatuses, a normally open alarm circuit common to said plurality ofapparatuses, a relay for controlling said alarm circuit, each of saidapparatuses having coordinated thereto a signal circuit for actuatingsaid relay, a control circuit independent of said relay and a contactdevice having means movable in response to changes of a selectedcondition in the apparatus so as to activate said signal circuit as wellas said control circuit upon the occurrence of an abnormality of saidcondition and to interrupt said control circuit when the condition inthe apparatus is restored to normal, said control circuit includingmeans for rendering its coordinated signal circuit, independently ofsaid contact device, inoperative on said relay for the duration of saidabnormality, and shutter means operatively connected with said movablemeans of said contact device to move in response to the movements ofsaid movable means.

13. In an electric alarm system for the supervision of a plurality ofapparatuses, a normally open alarm circuit common to said plurality ofapparatuses, a relay for controlling said alarm circuit, each of saidapparatuses having coordinated thereto a signal circuit for actuatingsaid relay, a control circuit independent of said relay and a contactdevice having means movable from a neutral position in either of twodirections in the period said holding contact and said thermal switchare closed and thereby said heater coil is operative to open saidthermal switch.

11. In an electric alarm system for the supervision of a plurality ofapparatuses, a normally open alarm circuit common to said plurality ofapparatuses, a relay for controlling said alarm circuit, each of saidapparatuses having coordinated thereto a signal circuit for actuatingsaid relay, a control circuit independent of said relay, a normallyclosed thermal switch in said signal circuit, a heater coil in operativeposition with regard to said thermal switch forming part of said controlcircuit, and a contact means adapted to keep said signal circuit as wellas said control circuit inactive as long as the condition in thecoordinated apparatus is normal and to activate both said circuits uponthe occurrence of an abnormality of said condition, the heater coil insaid control circuit, upon the latter being so activated, opening with atime lag its coordinated thermal switch and keeping it open until thecondition in the apparatus is restored to normal whereby said contactdevice is caused to break said control circuit so as to release saidsignal response to changes of a selected condition in the apparatus soas to activate said signal circuit as well as said control circuit uponthe occurrence of an irregularity in said condition in either directionas compared with the condition prescribed as regular and to interruptsaid control circuit when the condition in the apparatus is restored toregular, said control circuit including means for rendering itscoordinated signal circuit, independently of said contact device,inoperative on said relay for the duration of said abnormality, andshutter means operatively connected with said movable means of saidcontact device to move in unison with and in the same sense as saidmovable means.

ALBERT F. SPERRY.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 1,781,497 Crago Nov. 11, 19301,789,566 Spray Jan. 20, 1931 2,127,343 Parlett Aug. 16, 1938 2,278,939Muehter Apr. 7,1942

